Thermionic amplifier



Dec. 3, 1929. H. TRUMP 1,738,408

THERMIONIC AMPLIFIER Filed Dec. 24, 1926 I AMPLIFIER INVENTOR EDWARDHERBERT TRUMP TTORNEY Patented Dec. 3, 1929 UNITED I STATES UPAITENTKOFFICE -EDWA3D HERBERT 1 3m, OII LONDON, ENGLAND, ASSIGNOB TO RADIOCOBPOEATIOR O1 AMERICA, A CORPORATION OF DELAWARE TEERIIONIC AMPLIFIERApplication fled December 24, 1320, Serial No.

This invention relates to thermionic amplifiers and is particularlysuitable for use with repeaters of the kind used, for example, on boardship to repeat in one part of the ship a a musical programme or the likewhich is given in another part of the ship. In such cases there isusually available an ample sup-' ply of electric power from dynamoelectric machines, but, as iswell known, the presence of commutatorripple and other variations in potential render such power unsuitablefor direct use in known amplifiers. One of the objects of the presentinvention is to provide an amplifier which can make use of such powerwith a minimum of interference by undesired noise.

According to this invention chokes are inserted in the power supply tothe cathode and in an effective grid circuit on the input side of theamplifier, the said chokes being coupled to one another. Preferably thedegree of coupling is made variable and one or both of the chokes is orare provided with a variable shunt resistance. Preferably also theanodepower supply is obtained from a dynamo-electric machine through anarrangement of smoothing chokes and condenscrs.

The invention is illustrated in the accompanying drawing, in whichFigure 1 is a schematic circuit diagram, and Figure 2 is a diagrammaticplan view of one form of construction.

In the form of construction illustrated in the figures which show theinvention as applied to a multistage thermionic amplifier indicateddiagrammatically within the dotted lines and which may be of any of theknown types, for instance, resistance-coupled, transformer-coupled,etc., the cathodes 1 of the valves are supplied with direct current froma dynamo-electric machine 2 subject to slight potential variations, andin one of the main leads from the said machine lS inserted a choke 3.The grid input 4 to the amplifier is efiectcd, through a transformer 5and in series with the secondary of the said transformer and with thegrid bias battery C (if desired) is inserted a second choke 6,

5 which is coupled to the first choke 3 and plates are connected inparallel constituting supply. The resistances shown adjacent the156,813, and in- Great was; January 9, 192a,

across which is connecteda variable shunt resistance 7. The remainder ofthe'circuit shown in Figure 1 indicates that of a known amplifierarrangement, those valves whose a multi-valve last stage amplifier, thetransformer on the extreme right of the figure being the outputtransformer of this stage, while the transformer to the left of theoutput transformer is the grid transformer for said stage. The chokecoil3is fornied by windings on the two limbs of a U-shaped core 8, andthe choke coil 6 is formed by a winding on a straight open core 9. Thetwo chokes arecarried on a base plate so that the straight core 9 is atright angles to the limbs of the U-shaped core 8. One ofvthe chokes,preferably that with the straight core 9, is arranged to be able to bemounted in. any of a plurality of mounting holes 10, so that it may beadjusted and fixed by means of screws 11, in the position which givesthe best degree of coupling. In practice it has been found that a rathersmall degree of coupling is sulficient, and in this arrangement thenecessary coupling is obtained by the linking of the leakage fields fromthe cores of the chokes.

The anodes 12 of the valves are su plied from a separate high tensiondynamo-e ectric machine 13 to the negative terminal of which the valvefilaments are connected in any known way, as by earthing. Asmoothingcondenser 14 is connected across the said ma chine, and in theleads to the anodes of certain of the valves smoothing chokes 15 .areinserted. A condenser 16 is connected between the anode side of eachsmoothing choke and the negative terminal of the high tension anodes 12of the first two valves indicate the usual so-called couplingresistances. In some cases the provision of smoothing chokes andassociated condensers may not be necessary for the anodes of all thevalves in'the amplifier.

The choke in the grid circuit and that in the filament lighting circuitmust be coupled together in a direction such that the noises caused byripple. in the filament current-are annulled b voltage rip 1e. ap liedto the grid, for o viously if t e an chokes are coupled in the otherdirection, the noises will only be made worse. The action of these twoimpedances is simply that they enable a suitable variable voltage to beap lied to the grid to entirely counterbalance t e effect of the varyingvoltage on the filaments. i

he correct working of the device obviously depends in some measure onobtaining a volt.- age. of very flat wave form on the first grid of theamplifier, and having a comparatively big lag relative to the currentvariations in the filaments, to correspond as nearly as possible to thevariation in temperature (at ripple freguency) of the said filaments.

Having now particularly described the nature of my invention, what Iclaim is l. A thermionic ampllfier arrangement,

,comprising cathodes adapted to be heated by the power supply of adynamo-electric machine, a choke coil in the lead to said cathodes, anda second choke coil in the grid circuit on the input side of theamplifier coupled to said first-mentioned coil, whereby interference bycommutator ripple from the supply source is suppressed or minimized.

2. The arrangement as set forth in claim 1, one of said chokes beingprovided with a U-shaped core and the other of said chokes beingprovided with a straight core, the coupling being effected by linkage ofthe leakage fields from the cores of said chokes.

3. A thermionic amplifier arrangement, comprising cathodes adapted to beheated by the power supply of a dynamo-electric machine, a choke coil inthe lead to said cathodes, and a second choke coil in the grid circuiton the input side of the amplifier coupled to said first-mentioned coil,the coupling between said chokes being variable.

4. A thermionic amplifier arrangement,

comprising cathodes adapted to be heated by the power supply of adynamo-electric machine, a choke coil in the lead to said cathodes, anda second choke coil in the grid circuit on i the input side of theamplifier coupled to said first-mentioned coil, one of said chokes beingadapted to be mounted in any of a plurality of positions with respect tothe other choke, thereby varying the coupling therebetween.

5. A thermionic amplifier arrangement comprising a plurality ofcathodes, a choke coil in the lead to said cathodes, a second choke coilin the grid circuit on the input side of the amplifier coupled to saidfirst-mentioned coil, and a variable resistance shunting one of saidchokes.

6. A thermionic tube arrangement comprising an element adapted to beheated-by a direct current source subject to slight potential variationsfor producing electron emission, an inductance coil in a lead to saidelement, and a second inductance coil connected to another element ofsaid tube and 7. A thermionic tube arran ement comprising an elementadapted to heated by a direct current source subject to slight potentialVflIlfliliODS forv producing electron emission, an inductance coilconnected in a lead to said element, and a second inductance coilconnected tothe grid ofsaid tube and coupled to the first mentionedinductance for minimizing effects due to the potential variations ofsaid current source.

A thermionic tube arrangement comprlsmg an element adapted 'to be heatedby a direct current source subject to'slight potential variations forproducing electron emission, an inductance coilconnected in a lead tosaid element, and a second inductance coil connected to the grid of saidtube and adjustably coupled to the first mentioned inductance forminimizing effects due to slight potential variations of said currentsource.

A thermionic tube arran ement comprising an element adapted to e heatedby a direct current source subject to slight potential variations forproducing electron emission, an inductance coil in a lead to saidelement, a second inductance coil connected to another element of saidtube and coupled

